Charging C4 Battery using jumper positions

[Cody Forbes]

Isnt the fault memory still volatile? That's a good indicator (although still not defacto) that it doesn't have connection to terminal 30, only to 15.

-Cody (mobile)

On Aug 2, 2011, at 10:24 PM, Mark Rosenkrantz <speedracer.mark at gmail.com> wrote:

> I think all Motronic and newer ECUs have batt+ lines, from memory.   How it switches internally, I don't know.
>  
> Mark Rosenkrantz
> 
> On Tue, Aug 2, 2011 at 10:06 PM, Cody Forbes <cody at 5000tq.com> wrote:
> Technically if, while charging at 30-40 amps, your battery voltage exceeds 15.5 volts then you have a battery with sulfated plates that needs to be replaced. Your ECU should be able to handle that much voltage during that period. I've seen voltage at 16v for short periods of time when I had to nurse one of my cars home with a bad voltage regulator, it would spike high and I'd add some loads (lights, defroster etc) to draw it low then after a few minutes it would start going low so I had to turn the loads off etc. ECU still functions properly a year later.
> 
> Thinking about that a bit more your ECU shouldn't see any voltage anyways. IIRC With the ignition switched off the ECU on a C4 is not connected to any power sources (C4/urS guy please confirm). I know to be a fact on the older Hitachi ECU equipped cars, but the Bosch ECU *might* have a constant power line.
> 
> -Cody (mobile)
> 
> On Aug 2, 2011, at 9:53 PM, Jay M <jaybird002 at msn.com> wrote:
> 
> >
> > Thanks Tony, Huw, Steve, Christopher, Mike, Eric & Mark for your responses. I guess I am a creature of habit with both new generation and old gen cars. That is to say, when I encountered the rare dead battery in one of my cars, and when I say "dead" I mean really drained to the point where there is absolutely no power left in the battery to illuminate even the smallest 1 watt dash light (which was the case today)..... I always removed the battery to charge it back up with a battery charger to at least 12.5V in order to save the alternator the work and strain of recharging the battery. In addition, I guess another reason for me and perhaps more importantly, was I have read horror stories on other forums regarding charging batteries in cars equipped with an ECU where the ECU was fried due to supposedly overcharging of the battery while the battery was connected. Subsequently, I was always hesitant to charge the battery while it was connected to the car for fear of overchargin
>  g
> > and consequently frying the ECU.
> >
> > Date: Tue, 2 Aug 2011 16:20:42 -0500
> > Subject: Re: Charging C4 Battery using jumper positions
> > From: auditony at gmail.com
> > To: jaybird002 at msn.com
> > CC: quattro at audifans.com
> >
> >
> >
> >
> > I was under the inpression VAG did that changeover in 2000, so I'm surprised it remembered the code.
> >
> > Yes, you can charge the car just as jumping it, from those posts. It's a direct link to the battery, so it will work just the same as hooking directly on the battery.
> >
> > Tony
> >
> >
> > On Tue, Aug 2, 2011 at 3:41 PM, Jay M <jaybird002 at msn.com> wrote:
> >
> >
> >
> > Hello everybody,
> >
> >
> >
> > Just curious, on our 1996 A6 my wife left the key in the ignition in the first on position overnight and needless to say the battery was totally dead this morning upon startup. I removed the battery from underneath the rear seat and used my trusty old Sears 6 amp battery charger for a 6 hour charge on the work bench. My question is in the future if I need to charge the battery using this battery charger can I just charge the battery using the emergency battery jump positions under the hood near passenger side firewall....that is to say the positive lead from charger to positive emergency jumper post (underneath black plastic cover) and negative lead from battery charger to good chassis ground up front?
> >
> >
> >
> > Also, I was surprised upon reinstalling battery that I did not have to input my radio code for the original Bose stereo. The radio turned on fine and did not display the usual CODE message telling me to input the radio code. All my other present and previous C4's are and have been 1995's so this is the first Audi C4 I had that did not require the code when the battery was disconnected and then reconnected. Is this normal for a 1996? Thanks.
> >
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